RTCRtpSender with track behind RuntimeEnabled flag

third_party/WebKit/Source/modules/peerconnection/RTCRtpSender.cpp

Index: third_party/WebKit/Source/modules/peerconnection/RTCRtpSender.cpp
diff --git a/third_party/WebKit/Source/modules/peerconnection/RTCRtpSender.cpp b/third_party/WebKit/Source/modules/peerconnection/RTCRtpSender.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..c31fd2c73f47fcccd1e9033f7bc6c87d6ddca3ab
--- /dev/null
+++ b/third_party/WebKit/Source/modules/peerconnection/RTCRtpSender.cpp
@@ -0,0 +1,29 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "modules/peerconnection/RTCRtpSender.h"
+
+#include "modules/mediastream/MediaStreamTrack.h"
+
+namespace blink {
+
+RTCRtpSender::RTCRtpSender(std::unique_ptr<WebRTCRtpSender> sender,
+                           MediaStreamTrack* track)
+    : sender_(std::move(sender)), track_(track) {
+  DCHECK(sender_);
+  DCHECK(track_);
+}
+
+MediaStreamTrack* RTCRtpSender::track() {
+  DCHECK((track_ && sender_->Track() &&
+          sender_->Track()->Id() == static_cast<WebString>(track_->id())) ||
+         (!track_ && !sender_->Track()));
+  return track_;
+}
+
+DEFINE_TRACE(RTCRtpSender) {
+  visitor->Trace(track_);
+}
+
+}  // namespace blink